1. Field of the Invention
The present invention is concerned with a novel method of imparting nondurable soil release and soil repellency properties to textile materials. In one variant, the invention is concerned with a method of laundering soiled textile materials wherein the washed and rinsed textile material is thereafter treated to impart nondurable soil release and soil repellency properties. The invention further provides the improved textile material prepared by the method of the invention.
2. Prior Art
Natural textile fibers such as cotton and wool exhibit no soil repellency properties in the untreated state. However, the fibers are hydrophilic and water swellable and have excellent soil release properties when washed in an aqueous alkaline medium containing a detergent. Thus, while natural cotton and wool fibers are easily soiled, they are also easily cleaned.
Manmade textile fibers, on the other hand, are hydrophobic in nature and exhibit no soil release or soil repellency properties in the untreated state. As a result, textile fibers such as polyesters, rayon and nylon soil easily and are difficult to clean once soiled due to the lack of satisfactory soil release properties. The manmade fibers present a severe problem with respect to effective laundering and the problem is especially pronounced with blends of polyester and cotton fibers. When an oil stain such as motor oil impinges upon the surface of the resulting fabric, surface interaction forces and capillary forces tend to disperse the oil stain. Microscopic observations reveal that the oil stain coats the surfaces of the textile fibers throughout the soiled area. Elevated temperature is very detrimental as the oil molecules are forced deep into the polymer matrix and the resulting soiled fabrics are almost impossible to clean.
The surface characteristics of both manmade and natural textile fibers have been modified heretofore by applying various types of soil release or soil repellent finishes. When a particular type of finish is applied, a new solid surface is formed on the textile fibers. Intrinsic interaction between the fibers and the staining substance no longer exists as new interaction forces between the applied finish and the stain predominate. By applying a continuous film of a hydrophilic water swellable polymer over the normally hydrophobic surfaces of manmade fibers, the resulting fiber surfaces are rendered hydrophilic and water swellable when laundered and the soil is released effectively. Thus, the soiled manmade fabric regains its original appearance after a single washing.
Another approach to the laundering problem has been to impart soil repellency properties to the textile fibers and thereby prevent or reduce soiling in the first instance. A number of soil repellent finishes have been proposed heretofore. The most effective soil repellent finishes are usually fluorochemical finishes of the types sold under tradenames such as Zepel-B, F.C. 208, and ACTM. The fluorochemical finishes impart good oil and water repellency properties to both natural and manmade textile fibers. The oleophobicity and hydrophobicity properties imparted by the conventional fluorocarbon finishes may be attributed to the surface energy caused by close packing of the fluoro groups at the fiber interfaces. Textile fibers coated with a soil repellent fluorocarbon finish are hydrophobic in nature and exhibit very poor or no soil release properties. While the soil repellent finishes are effective in repelling soil and reduce the frequency of laundering, nevertheless once soiled the fabric is very difficult to launder.
A number of attempts have been made to overcome the soil release deficiencies of the fluorocarbon finishes. One approach to the problem was to use a fluorochemical which has a hydrophobic soil repellent fluorocarbon moiety and a hydrophilic soil release moiety incorporated in a single molecule or molecular chain.
While these recently developed fluorochemical finishes have met with some degree of success, nevertheless they do have deficiencies when applied in accordance with prior art processes. The fluorochemicals are expensive and heretofore had to be applied to the fabric in relatively large amounts to impart effective soil repellent properties As a result, the prior art has concentrated its efforts on the application of durable soil repellent finishes. The soil repellent properties diminish with each laundering and thus the fluorochemical does not provide optimum protection after the initial washing and eventually becomes ineffective. The soil release properties likewise diminish with each laundering and eventually the fabric cannot be laundered effectively.
Satisfactory nondurable finishes which impart optimum soil release and soil repellent properties have not been available heretofore. One deterrent was the high costs of application by the prior art processes and the fact that the finish is largely removed with each laundering. If a nondurable soil release and soil repellent finish is to be commercially acceptable it should be capable of being applied at low cost and it should provide optimum soil release and soil repellency properties throughout its lifespan. A suitable nondurable finish of this type was not available heretofore in spite of the advantages thereof over the durable type of finishes which are characterized by diminished effectiveness with age.